This program undertakes coordinated biological, biochemical and immunological laboratory measurements on 1000 primary human mammary neoplasms and on their metastases. It aims to relate these findings to the physiological status and the subsequent course and therapeutic responses of the subject patients in order to develop understanding of the metastatic process and of the mechanisms of regression induced by radiation therapy and by systemic treatments. It will undertake similar characterizations of benign proliferative mammary lesions and will attempt to identify pre-neoplastic states by relating these findings to the primary tumor analyses.